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Data for: Patrolling the border: billfish exploit the hypoxic boundary created by the world's largest oxygen minimum zone

Logan, Ryan K.1

Published Apr 27, 2023 on Dryad. https://doi.org/10.5061/dryad.r7sqv9sj4

Data files

Apr 27, 2023 version files 275.18 MB

Abstract

  1. Pelagic predators must contend with low prey densities that are irregularly distributed and dynamic in space and time. Based on satellite imagery and telemetry data, many pelagic predators will concentrate horizontal movements on ephemeral surface fronts—gradients between water masses—because of enhanced local productivity and increased forage fish densities.
  2. Vertical fronts (e.g., thermoclines, oxyclines) can be spatially and temporally persistent and aggregate lower trophic level and diel vertically migrating organisms due to sharp changes in water density or available oxygen. Thus, vertical fronts represent a stable and potentially energy-rich habitat feature for diving pelagic predators but remain little explored in their capacity to enhance foraging opportunities.
  3. Here, we use a novel suite of high-resolution biologging data, including in situ derived oxygen saturation and video, to document how two top predators in the pelagic ecosystem exploit the vertical fronts created by the oxygen minimum zone of the eastern tropical Pacific.
  4. Prey search behavior was dependent on dive shape, and significantly increased near the thermocline and hypoxic boundary for blue marlin (Makaira nigricans) and sailfish (Istiophorus platypterus), respectively. Further, we identify a behavior not yet reported for pelagic predators, whereby the predator repeatedly dives below the thermocline and hypoxic boundary (and by extension, below the prey). We hypothesize this behavior is used to ambush prey concentrated at the boundaries from below.
  5. We describe how habitat fronts created by low-oxygen environments can influence pelagic ecosystems, which will become increasingly important to understand in the context of global change and expanding oxygen minimum zones. We anticipate that our findings are shared among many pelagic predators where strong vertical fronts occur, and additional high-resolution tagging is warranted to confirm this.